Apparatus and method for active vibration control of hybrid electric vehicle

ABSTRACT

The present disclosure relates to active vibration control of a hybrid electric vehicle. One form provides a method that may include setting up a period of fast Fourier transform (FFT) and performing FFT of an engine speed or a motor speed corresponding to the period of the FFT from a reference angle signal; setting up a reference spectrum; extracting vibration components to be removed based on information of the reference spectrum; selecting and adding a removal object frequency from the vibration of each frequency and performing inverse FFT; determining a basic amplitude ratio according to the engine speed and the engine load; determining an adjustable rate which decreases an anti-phase torque as a change amount of the engine speed is decreased; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.15/261,348, filed on Sep. 9, 2016, which claims priority to KoreanPatent Application No. 10-2015-0177460, filed in the Korean IntellectualProperty Office on Dec. 11, 2015, the entirety of all of which areincorporated by reference herein.

BACKGROUND (a) Field of the Disclosure

The present disclosure relates to an apparatus and a method for activevibration control of a hybrid electric vehicle. More particularly, thepresent disclosure relates to an apparatus and a method for activevibration control of a hybrid electric vehicle that controls unsteadyvibration by analyzing a frequency spectrum through fast Fouriertransform (FFT).

(b) Description of the Related Art

A hybrid vehicle is a vehicle using two or more different kinds of powersources, and is generally a vehicle that is driven by an engine thatobtains a driving torque by burning fuel and a motor that obtains adriving torque with battery power.

Hybrid electric vehicles can be provided with optimum output torque,depending on how the engine and the motor are operated while thevehicles are driven by the two power sources, that is, the engine andthe motor.

Hybrid electric vehicles may form various structures using the engineand the motor as power sources, and hybrid electric vehicles areclassified as a TMED (Transmission Mounted Electric Drive) type, inwhich the engine and the motor are connected by an engine clutch and themotor is connected to the transmission, and an FMED (Flywheel MountedElectric Drive) type, in which the motor is directly connected to acrankshaft of the engine and connected to the transmission through aflywheel.

From among these, since the FMED type of the hybrid electric vehicle isvery noisy and has severe vibration, vibration reduction thereof isbeing studied. A method of frequency analysis which extracts thevibration component is normally used for this.

An analog method using a band pass filter has been used in aconventional frequency analysis, wherein the analog method of analysisdetermines whether or not a frequency is abnormal based on an amplitudeof each expected point of a frequency band.

However, distinguishing between the vibration component of the engineand the vibration of the noise component is difficult, and unnecessaryover-control of the vibration negatively affects aspects of controlefficiency and energy management. Further, because it is only possibleto create and synchronize a reference signal with respect to a specificfrequency in the conventional frequency analysis, comprehensive andactive control of other frequencies which may be additionally generatedis not performed.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present disclosure has been made in an effort to provide anapparatus and a method for active vibration control of a hybrid electricvehicle, having advantages of elaborately controlling an abnormalvibration component through an entire frequency spectrum analysis usingFFT (fast Fourier transform) and reflecting a change of a surroundingfrequency component in real time by feedback.

An exemplary form of the present disclosure provides a method for activevibration control of a hybrid electric vehicle that may includedetecting an engine speed or a motor speed; selecting a reference anglesignal based on position information of a motor or an engine; setting upa period of fast Fourier transform (FFT) and performing FFT of theengine speed or the motor speed corresponding to the period of the FFTfrom the reference angle signal; setting up a reference spectrumaccording to an engine speed and an engine load; extracting a vibrationcomponents to be removed based on information of the reference spectrum;selecting and adding a removal object frequency from the vibration ofeach frequency and performing inverse FFT; determining a basic amplituderatio according to the engine speed and the engine load; determining anadjustable rate which decreases an anti-phase torque as a change amountof the engine speed is decreased; and performing active vibrationcontrol of each frequency based on the information of the basicamplitude ratio, the adjustable rate, and the engine torque.

The reference angle signal may be set by dividing by a number (m) ofresolver poles based on information of the position of the motor or setup the reference angle between top dead center (TDC) and bottom deadcenter (BDC) of the number one cylinder or the number four cylinderbased on information of the position of the engine.

The FFT period may be set in consideration of a cylinder and a stroke ofthe engine.

The analysis of the FFT signal may calculate a amplitude and phaseinformation of each frequency.

The frequency component that the FFT signal is greater than thereference spectrum may be selected as the vibration component to beremoved.

The vibration component to be removed is removed by outputting the motortorque corresponding to an inverse value of a value by multiplying areference signal obtained by inverse FFT, the engine torque, the basicamplitude ratio and the adjustable rate.

Another exemplary form of the present disclosure provides a controlapparatus for active vibration control of a hybrid electric vehicleincluding an engine and a motor as a power source that may include aposition sensor configured to detect position information of the engineor the motor; and a controller configured to select a reference anglesignal on the basis of a signal from the position sensor, perform fastFourier transform (FFT) analysis, extract a vibration component to beremoved through the FFT analysis, generate a reference signal byperforming inverse FFT, and perform active vibration control of eachfrequency by reflecting a basic amplitude ratio, a predeterminedadjustable rate which decreases an anti-phase torque as a change amountof the engine speed is decreased, and an engine torque to the referencesignal.

The controller may set up a reference spectrum according to an enginespeed and an engine load, and extract the vibration component to beremoved by comparing the reference spectrum with the FFT signal.

The controller may generate the reference signal by performing inverseFFT after selecting and summing a removal object frequency from eachfrequency vibration through FFT analysis.

The controller may remove the vibration component to be removed byoutputting the motor torque corresponding to an inverse value of a valueby multiplying the reference signal generated created by the inverseFFT, the basic amplitude ratio, the adjustable rate, and the enginetorque.

The controller may set up the reference angle signal by dividing by anumber (m) of resolver poles based on information of the position of themotor or set up the reference angle between top dead center (TDC) andbottom dead center (BDC) of a number one cylinder or a number fourcylinder based on information of the position of the engine.

The controller may set up an FFT period in consideration of a cylinderand stroke of the engine, and analyzes the FFT signal by a calculatedamplitude and phase information of each frequency.

As described above, according to the exemplary form of the presentdisclosure, the vibration may be actively controlled, because the exactvibration component of each frequency may be extracted through FFTfrequency spectrum analysis. Therefore, since the determination systemof the reference angle of the engine and the motor may be utilized as itis, an additional device or an algorithm for signal synchronization asused in the conventional art may be eliminated.

In addition, the adjustment amount of vibration and frequency which isthe object of the vibration control may be controlled individually, itis possible to prevent inefficiency which is from the control when thevibration is over-removed and the fuel consumption may be improved asthe motor torque is increased when the engine is accelerated. Thus,precise and efficient active control may be performed through thefeedback control in real time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle.

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle.

FIG. 3 is a drawing illustrating vibration reduction to which a methodfor active vibration control of a hybrid electric vehicle is applied incase that a change amount of an engine speed is decreased.

FIG. 4A is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

FIG. 4B is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

FIG. 4C is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

FIG. 4D is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

FIG. 4E is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

FIG. 4F is a graph for explaining a method for active vibration controlof a hybrid electric vehicle is applied.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplary forms ofthe present disclosure have been shown and described, simply by way ofillustration. As those skilled in the art would realize, the describedforms may be modified in various different ways, all without departingfrom the spirit or scope of the present disclosure.

Throughout this specification and the claims which follow, unlessexplicitly described to the contrary, the word “comprise” and variationssuch as “comprises” or “comprising” will be understood to imply theinclusion of stated elements but not the exclusion of any otherelements.

Like reference numerals designate like elements throughout thespecification.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general includinghybrid vehicles, plug-in hybrid electric vehicles, and other alternativefuel vehicles (e.g., fuels derived from resources other than petroleum).As referred to herein, a hybrid electric vehicle is a vehicle that hastwo or more sources of power, for example both gasoline-powered andelectric-powered vehicles.

Additionally, it is understood that some of the methods may be executedby at least one controller. The term “controller” refers to a hardwaredevice that includes a memory and a processor configured to execute oneor more steps that should be interpreted as its algorithmic structure.The memory is configured to store algorithmic steps and the processor isspecifically configured to execute said algorithmic steps to perform oneor more processes which are described further below.

Furthermore, the control logic of the present disclosure may be embodiedas non-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor, acontroller, or the like. Examples of computer readable media include,but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetictapes, floppy disks, flash drives, smart cards, and optical data storagedevices. The computer readable recording medium can also be distributedin network coupled computer systems so that the computer readable mediaare stored and executed in a distributed fashion, e.g., by a telematicsserver or a controller area network (CAN).

An exemplary form of the present disclosure will hereinafter bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle.

As shown in FIG. 1, an apparatus for active vibration control of ahybrid electric vehicle includes an engine 10, a motor 20, a positionsensor 25, a clutch 30, a transmission 40, a battery 50, and acontroller 60.

The engine 10 outputs power by combusting fuel as a power source whileturned on. The engine 10 may be various disclosed engines such as agasoline engine or a diesel engine using conventional fossil fuel. Therotation power generated from the engine 10 is transmitted to thetransmission 40 side through the clutch 30.

The motor 20 is operated by a 3-phase AC voltage applied from thebattery 50 through an inverter to generate torque, and operates as apower generator and supplies regenerative energy to the battery 50 in acoast-down mode.

In the exemplary form of the present disclosure, the motor 20 may bedirectly connected to the crankshaft of the engine 10.

The position sensor 25 detects position information of the engine 10 orthe motor 20. That is, the position sensor 25 may include a crankshaftposition sensor that detects a phase of the crankshaft or a motorposition sensor that detects a position of a stator and a rotor of themotor. The controller 60 may calculate an engine speed bydifferentiating the rotation angle detected by the crankshaft positionsensor, and a motor speed may be calculated by differentiating theposition of the stator and the rotor of the motor detected by the motorposition sensor. The position sensor 25 may be additional speed sensor(not shown) for measuring the engine speed or the motor speed.

The clutch 30 is disposed between the motor 20 connected to thecrankshaft of the engine 10 and the transmission 40, and switches powerdelivery to the transmission 40. The clutch 30 may be applied as ahydraulic pressure type of clutch or dry-type clutch.

The transmission 40 adjusts a shift ratio according to a vehicle speedand a running condition, distributes an output torque by the shiftratio, and transfers the output torque to the driving wheel, therebyenabling the vehicle to run. The transmission 40 may be applied as anautomatic transmission (AMT) or a dual clutch transmission (DCT).

The battery 50 is formed with a plurality of unit cells, and a highvoltage for providing a driving voltage to the motor 20 is stored at thebattery 50. The battery 50 supplies the driving voltage to the motor 20depending on the driving mode, and is charged by the voltage generatedfrom the motor 20 in the regenerative braking.

The controller 60 selects a reference angle signal on the basis of asignal from the position sensor 25, performs fast Fourier transform(FFT), extracts a vibration component to be removed through the FFTanalysis, generates a reference signal by performing inverse FFT, andperforms active vibration control of each frequency by reflecting abasic amplitude ratio, a predetermined adjustable rate such that ananti-phase torque is decreased as a change amount of the engine speed isdecreased, and an engine torque to the reference signal. The referencesignal may mean an inverse FFT signal of the vibration components to beremoved according to frequencies.

For these purposes, the controller 60 may be implemented as at least oneprocessor that is operated by a predetermined program, and thepredetermined program may be programmed in order to perform each step ofa method for active vibration control of a hybrid electric vehicleaccording to an exemplary of the present invention.

Various embodiments described herein may be implemented within arecording medium that may be read by a computer or a similar device byusing software, hardware, or a combination thereof, for example.

According to hardware implementation, the embodiments described hereinmay be implemented by using at least one of application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, and electric units designed toperform any other functions.

In software implementations, forms such as procedures and functionsdescribed in the present forms may be implemented by separate softwaremodules. Each of the software modules may perform one or more functionsand operations described in the present disclosure. A software code maybe implemented by a software application written in an appropriateprogram language.

Hereinafter, a method for active vibration control of the hybridelectric vehicle according to an exemplary form of the presentdisclosure will be described in detail with reference to FIG. 2 to FIG.4.

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle, and FIG. 3 is a drawing illustratingvibration reduction to which a method for active vibration control of ahybrid electric vehicle is applied in case that a change amount of anengine speed is decreased.

As shown in FIG. 2, an active vibration control method of the hybridelectric vehicle is started when the position sensor 25 detects positioninformation of the engine 10 or the motor 20 at step S100, and thecontroller 60 may detect engine speed or motor speed using the positioninformation of the engine 10 or the motor 20 at step S100 (refer to FIG.4A). The controller 60 selects the reference angle signal based on thesignal of the position sensor 25 at step S110. That is, the controller60 selects the reference angle signal according to information ofpositions of the engine 10 and the motor 30 (refer to FIG. 4A).

The controller 60 may set up the reference angle signal by dividing by anumber (m) of resolver poles based on information of the position of themotor 20, or may set up the reference angle signal between top deadcenter (TDC) and bottom dead center (BDC) of the number one cylinder orthe number four cylinder based on information of the position of theengine 10. For example, the controller 60 may select the reference anglesignal based on the information of the position of the motor 20, and maycreate the reference angle signal by dividing 16 poles signal into eight(8). The reference angle signal means a start point for performing FFT.

After that, the controller 60 sets up a period of the FFT for performingat step S120. The controller 60 may set up the entire period inconsideration of a cylinder and stroke of the engine 10. For example, ifthe engine 10 has four cylinders and four strokes, the crank angle maybe 720 degrees.

When the FFT period is set up in the step S120, the controller 60analyzes the FFT signal at step S130. That is, the controller 60performs the FFT of the engine speed, an engine acceleration, arotational period of the engine, the motor speed, a motor acceleration,or a rotational period of the motor corresponding to the period of theFFT from the reference angle signal (refer to FIG. 4B). The controller60 may calculate amplitude and phase information of each frequency byanalyzing the FFT signal.

In addition, the controller 60 sets up a reference spectrum according tothe engine speed and the engine load at step S140. That is, thecontroller 60 may set up a vibration reference value of each frequencyaccording to an operating point of the engine.

When the reference spectrum is set up in the step S140, the controller60 extracts a vibration component to be removed at step by comparing theFFT signal with the reference spectrum at step S150. That is, thecontroller 60 may select an object requiring vibration control in acompared result value of the FFT analysis and the predeterminedvibration reference value. The controller 60 may extract the frequencycomponent that the FFT signal is greater than the reference spectrum asthe vibration component to be removed. For example, referring to FIG.4B, f2 frequency component may be selected as a frequency component tobe removed. Since the reference spectrum means normal vibrationcomponents according to the engine speed and load, the controller 60determines the frequency component that the FFT signal is greater thanthe reference spectrum as abnormal vibration components to be removed.

As shown in FIG. 3, a amplitude and phase of vibration components ofeach frequency calculated by performing FFT analysis is illustrated inleft upper side of the drawing.

When the vibration components to be removed is selected in the stepS150, the controller 60 sums the vibration components to be removedaccording to frequencies, and performs inverse FFT to create a referencesignal at step S160 (refer to FIG. 4C). As described above, thereference signal means inverse FFT signal of the vibration components tobe removed.

When the reference signal is generated by performing the inverse FFT inthe step S160, the controller 60 determines a basic amplitude ratioaccording to the engine speed and the engine load at step S170. Herein,the basic amplitude ratio according to the engine speed and load may bedetermined in advance by a predetermined map.

In addition, the controller 60 determines an adjustable rate whichdecreases an anti-phase torque as a change amount of the engine speed isdecreased at step S180.

As shown in FIG. 3, the anti-phase torque which overlaps the componentof vibration to be removed is illustrated as a dotted line in left lowerside of the drawing. Herein, if the change amount of the engine speed isdecreased, the adjustable rate may be set up such that the anti-phasetorque is decreased in a negative direction as illustrated by a solidline.

After that, the controller 60 performs active vibration control based oninformation of the amplitude ratio, the adjustable rate, and the enginetorque at step S180. That is, the controller 60 may remove all thepositive components and negative components of the vibration componentsby outputting the motor torque corresponding to an inverse value of avalue by multiplying the reference signal created by inverse FFT, theengine torque and the basic amplitude ratio (refer to FIG. 4D). Sincethe reference signal is expressed as speed according to time, thecontroller 60 removes the vibration components to be removed byreflecting the engine torque and the basic amplitude ratio to thereference signal and transforming the reference signal to torquecomponent. That is, as shown in FIGS. 4E and 4F, it is possible tocontrol the engine speed or the motor speed that the frequencycomponents corresponding to the reference spectrum are remained.

Referring to FIG. 3, the adjustable rate is applied to the vibrationcomponent extracted through the FFT analysis, and since the decreasedanti-phase torque as the change amount of the engine speed is decreasedis added, it is controlled such that the object to be removed is removedand a required vibration component remains as described in right side ofthe drawing.

As shown in FIG. 4, if a vehicle is decelerating in which the changeamount of the engine speed is decreasing, the predetermined adjustablerate may be applied so as to decrease the anti-phase torque. At thistime, since vibration of the engine is decreased as the engine speed isdecreased, effect of vibration reduction can be maintained even thoughthe anti-phase torque is decreased in accordance with the adjustablerate. Therefore, vibration can be actively reduced with minimizingenergy consumption. Further, remained energy may be used for batterycharging.

As described above, the vibration may be actively controlled, becausethe exact vibration component of each frequency may be extracted throughFFT frequency spectrum analysis. Therefore, since the determinationsystem of the reference angle of the engine and the motor may beutilized as it is, an additional device or an algorithm for signalsynchronization as used in the conventional art may be eliminated.

In addition, the adjustment amount of vibration and frequency which isthe object of the vibration control may be controlled individually, itis possible to prevent inefficiency which is from the control when thevibration is over-removed and the fuel consumption may be improved asthe motor torque is increased when the engine is accelerated. Thus,precise and efficient active control may be performed through thefeedback control in real time.

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the disclosure is not limited to the disclosed forms. Onthe contrary, it is intended to cover various modifications andequivalent arrangements included within the spirit and scope of theappended claims.

What is claimed is:
 1. An apparatus for active vibration control of ahybrid electric vehicle including an engine and a motor, comprising: aposition sensor configured to detect position information of the engineor the motor; and a controller configured to: select a reference anglesignal based on position information detected by the position sensor,determine a fast Fourier transform (FFT) signal based on performing FFTon a detected engine speed or detected motor speed, wherein the FFTsignal includes a plurality of frequency components; extract one or morevibration components from the FFT signal; determine a summed removalobject by adding each of the extracted vibration components; generate areference signal by performing inverse FFT on the summed removal object;and perform active vibration control of each frequency component bycontrolling the engine speed or controlling the motor speed based on avalue calculated from a basic amplitude ratio, a predeterminedadjustable rate, an engine torque, and the reference signal.
 2. Theapparatus of claim 1, wherein the controller is configured to determinea reference spectrum covering the plurality of frequency componentsaccording to the engine speed and an engine load, and to extract the oneor more vibration components based on a comparison of the FFT signalwith the reference spectrum.
 3. The apparatus of claim 1, wherein thecontroller is configured to remove the vibration component by outputtinga motor torque corresponding to a negative value of a value bymultiplying the reference signal, the basic amplitude ratio, theadjustable rate, and the engine torque.
 4. The apparatus of claim 1,wherein the controller is configured to set up the reference anglesignal by dividing by a number of resolver poles based on information ofthe position of the motor or to set up the reference angle signalbetween top dead center (TDC) and bottom dead center (BDC) of a numberone cylinder or a number four cylinder based on information of theposition of the engine.
 5. The apparatus of claim 1, wherein thecontroller is configured to determine an FFT period based on engineattributes including a number of engine cylinders and a stroke of theengine, and analyze the FFT signal by a calculated amplitude and phaseinformation of each frequency component.